Urban Ecology: Stones or Rocks?

Why are there two words for mineral concretions?  And what does that have to do with urban ecology?

I recently visited Newark, NJ to work with BES urban design expert, Brian McGrath.  He lives in an the old industrial neighborhood of “The Ironbound,” and like many such places, there is great dynamism.  Some old buildings are being demolished, restaurants and clubs are being renovated in this place famous for Portuguese food, and the general rust down, fix up of lively urban places is much in evidence.  As we walked to a (strong!) coffee break during an afternoon of writing, I noticed a vacant lot that contained a big, smooth, ovoid boulder next to a yellow backhoe.  The lot sloped gently into the cellar hole of the missing building, and the rock and the backhoe were the only adornments I noticed in the fenced lot.

A Rock in the City

Why did I call it a rock, and not a stone?  This big rock with a grey, smooth surface was a remnant of the last glacial age.  It looked like nothing so much as a huge, water smoothed pebble – the sort of thing you could see on the bottom of a creek.  But this one was about a meter and a half long, and a meter wide.  It looked to be a little flattened, so that it would not roll easily.  Of course this rock was big enough so that it wouldn't roll easily in any event.

My big rock, was in fact a scaled up version of a

The Newark rock. Photo: Victoria Marshall

creek pebble, but the water in which the lonely Ironbound boulder was shaped was the water released by a mile-high mass of ice as it melted.  Such meltwater streams were huge, and they could carry rocks half the size of a first-generation suburban tract house.  Those streams tumbled the big and the small rocks that had been dislodged and trapped as the ice ground across the surface of northern North America some 20,000 years ago.  And this one was a good sized, but not a gigantic representative of glacial grinding followed by years of tumbling down the huge glacially fed precursor of the Passaic River.  The Passaic River is now a pretty respectable stream.  But when the glaciers were melting, it would have been much larger, and been joined to a sibship of other massive streams coursing toward the then distant Atlantic coast.  As the glaciers were exhausted by their own melting, the massive streams shrank and left deposits of mixed, smoothed sediments, pebbles, cobbles, and boulders. 

When I commented on the rock to Brian, he smiled and said that our landscape architect colleague, Victoria Marshall had also commented on the boulder.  Brian's remark went something like “you landscape people notice the same things.” 

Stones in the Country

Then I thought of another architect/ecologist story from some dozen years earlier.  Brian and Victoria were kind enough to include me as an ecological resource person in some of their urban design studios.  On one occasion, we arranged for some of the students to come up to the Cary Institute to work with me and fellow ecologist Mary Cadenasso.  I picked them up at the train station in Poughkeepsie, NY, and drove them the 13 miles on Rte 44 through the Dutchess County suburbs, engulfed agricultural mill towns, and exurban fringe with its regrowing, post-agricultural woods.  We drove down a small hill into the village center of Pleasant Valley, and as we turned the corner heading into town, we were presented with two architectural gems.  One was a two story, Art Deco switching station sitting amid huge power pylons and banks of muscular electrical transformers.  But a bit beyond the buff and black Art Deco treasure was a limestone barn, of much greater age.  The barn was large, had simple lines, just a few windows, a gable roof and the expected huge wooden doors in the side.  

One of the architects exclaimed aloud at the unexpected visual treat.  Now the “landscape” joke here is definitely on me, because I had been driving by that transformer yard for about 12 years before I even noticed the old barn.  Let’s give me a break and say it was because I was the ever cautious driver who always looked at the road.  But in reality, it was that I wasn't tuned into the built in this odd, now suburban site.  I was usually looking at the creek on the other side of the road – was it in flood, or was the water low?  Were there any lanky waterbirds standing by the bank?  Were the big sycamores on the eroding banks still upright?  Were the maple buds on the leafless branches expanding as the days got longer?  That kind of “landscape” ecology stuff.  To claim a little credit, I had actually finally noticed the stone barn a few years before the architecture student exclaimed over an unexpected and complex find.

Art Deco switching station lower left, old stone barn upper center.  Bing.com

Seeing Rocks and Seeing Stones

So there are two contrasts in these stories.  Rocks versus stones, and who sees rocks and who sees stones.  Rocks are generally considered those things out there in, on, and of the ground that are found where the volcanoes, rivers, glaciers, faults, uplift, and erosion left them.  They may have smooth or sharp edges depending on how long and how effectively water and wind have worked them, or whether the work has been dome by freezing and thawing of water in almost imperceptible cracks.

Stones on the other hand are things that have been shaped and arranged by people.  The stone barn was assembled from blocks of limestone quarried from very nearby.  Because many of the early colonial houses in the Hudson Valley are made of limestone, or sometimes roughly worked shale, I should not have been surprised to find an elegant, simple old barn constructed of limestone that could be obtained close by.  But even though limestone tends to fracture in relatively flat planes, there is some work in the quarrying.  And the shale and slate from one of the twisty formations of these rocks in Dutchess County, NY would likely have to undergo some hammer blows to make them fit better in building walls. 

Here's the big difference.  Stones may be found, but more likely worked, and them moved and arranged by people for their purposes.  That’s different from rocks, that just are, though they may be used pretty much as they are found sometimes.  Field walls are more likely an example of “use as found,” of course, since they don’t have to be weather-tight.  So the difference between stones and rocks says something about origin of the mineral conglomeration, the source of the energy shaping them, and whether there is purpose embodied in the shape.

It might be too easy to make a big deal out of an architect seeing buildings – stones; and an ecologist paying attention to other things at the same bend in the road.  Too easy to make a “thing” out of being excited by seeing an unexpected glacial relic a few blocks from the Newark train station.  Does one always have to see rocks OR stones? 

Saxa Loquuntur

Now we are back to urban ecology.  One could say that in the past, when urban ecology as a biological science was just getting started, it was conducted through the filter of seeing rocks in the city.  Looking for those places, processes, and entities that represented the unintentionality of nature motivated a lot of the earliest work by bioecologists in the city.  And it is very important to see this part of urban systems, as Anne Whiston Spirn suggested in her 1984 book, Granite Garden.  Cities work in part because there is natural work going on in and around them.  But her title also tells us that it is proper and necessary to see the built, the designed, the engineered, and the lived in as a part of an expanded view of urban ecology.  One has to see the stones of the city.  

The A. Hoen Lithography and Printing factory.  S. Pickett

But most urbanism in the past has focused only on the stones – the built fabric of cities – and ignored the biological processes that traditional ecology has pointed out to occur even in urban centers.  So it’s not a matter of stones versus rocks, but of a conversation that values both.  The pleasures of the architect joined with the pleasures of the ecologist, and the joys of the social scientist, as well, who help us understand how people live in and make decisions about our gardens of rock and stone.  As the bas reilef shield above the door of the now abandoned A. Hoen & Company lithography and printing shop in East Baltimore tells us, Saxa loquuntur - The stones are speaking to you. (http://www.zigersnead.com/current/blog/post/saxa-loquuntur-stones-and-stories-of-hoen-lithography/09-13-2011/3452/)  So are the rocks.  It’s a language that requires many differently trained ears to hear, and many voices to translate.  That’s today’s urban ecology.

BES II Project Outcomes

What's This All About?

Second story bays, Charles Village neighborhood, Baltimore.  BES LTER Photo.

BES, as a Long-Term Ecological Research project, is funded in six year increments.  BES II actually lasted for seven years due to a change in the scheduling of the grant cycle by the National Science Foundation (NSF).  We are obliged to produce a formal report to NSF that summarizes what we have done and what its broader impacts are.  This report is technical, encyclopedic, and detailed, and we will make it available when it is finished.  However, NSF also requires us to prepare a "plain language" summary which is posted on the Research.Gov website.  For the interest of the BES community, I'm posting that "Project Outcomes" report here.

A Premier Urban Research and Education Platform

Over the last seven years, the Baltimore Ecosystem Study (BES), Long-Term Ecological Research project has consolidated as a comprehensive, multidisciplinary platform for urban socio-ecological research.  It has demonstrated that concepts fundamental to mainstream ecology, such as the ecosystem, the watershed, and the shifting patch mosaic, help to understand the linked, human-natural components of cities, suburbs, and exurbs.  The knowledge generated has helped educate citizens and students about nature and natural processes in cities.  BES results have helped managers and policy makers 1) to identify new opportunities for urban watershed management, 2) to enhance urban tree canopy and its benefits, and 3) to employ ecological processes and amenities in neighborhood revitalization.  An important product is a new classification of urban land covers that combines social, physical, and biological features.

Sarah Ann Street, west Baltimore.  BES LTER Photo.

Knowledge About Ecosystem Processes

BES has produced new knowledge about urban stream behavior, documenting their disconnection from floodplain and ground waters.  It has shown increasing salt pollution in streams the long-term, and shown the effectiveness of stormwater “best management practices” in old residential neighborhoods.  Findings of stream research focused watershed management beyond the near-stream zone, and subsequent research on urban tree canopy documented reduced exposure to UVB radiation and reduction of the urban heat island effect.  The urban heat island has been shown to be very patchy in its potential negative effects on people, and hotspots of urban heat are distributed inequitably throughout the metropolis.  Other pollutants beyond heat are also patchy, with nitrogen deposited from traffic exhaust being both higher in general magnitude than expected, and concentrated around travel corridors.  The capacity of the urban system to absorb carbon (C) dioxide has also been documented, and daily and weekly patterns confirm the relationship of C dynamics to the activity patterns work and travel.  The vegetation in Baltimore results in less release of C to the environment than would occur without trees and lawns.

Biodiversity and Spatial Dynamics

The biological organisms other than people also have important roles in the urban ecosystem.  The identity of some animals has been homogenized across different cities, as expected, but local specialization still exists.  Urban soils contain a rich community of native and introduced species that contribute to soil metabolism and to the absorption of carbon dioxide and nitrates, taking these polluting compounds out of circulation.  New communities of aquatic animals establish in the novel habitats of stormwater detention ponds, and provide nutrient cycling services and support foodchains.  Notable members of some aquatic habitats are the introduced mosquitoes that can transmit West Nile virus (WNV) from birds to people.  The composition of mosquito communities shifts from rural to urban waters and containers, increasing the risk of WNV in the city.  Birds have been shown in other cities to depend upon the wealth of neighborhoods, but in Baltimore bird diversity responds to the structure of the tree canopy in different neighborhoods. 

Socio-Ecological Processes

BES research has evaluated other important interactions between the social and the biological ecology of Baltimore.  BES social scientists have discovered how the distribution of environmental "goods," such as parks and street trees, has changed over time in Baltimore, and how access to these amenities has varied among different groups.  Results show that African Americans in Baltimore today enjoy a high degree of access to parks and playgrounds compared to African Americans in other U.S. cities.  Examination of the history of environmental zoning variances documented inequitable decision making in Baltimore's past.  However, our research also shows that Black Baltimoreans are the beneficiaries of an "inherited" landscape.  In fact, a long history of segregation, both formal and informal, limited African American access to parks and playgrounds until large numbers of white residents left the city in the 1950s and 1960s.  It was only then that the city's black population "spread out," gaining access to park facilities once considered off limits.  An unexpected legacy of segregation is the contemporary association of toxic release inventory sites with white, working class neighborhoods.  Although areas of greater tree cover have less crime, not all residents consider urban trees to be an amenity.  For decades, both black and white residents of East Baltimore have opposed municipal tree-planting efforts.  In contrast, neighborhood associations during the first half of the 20th century were adept at attracting amenities, such as new street trees, while keeping out unwanted land uses.  BES social scientists adopted the theory of market segmentation to document the role of lifestyle differentiation as a key to understanding the shift from an industrial to a knowledge and service based economy in Baltimore. 

Riparian sycamore along the Gwynns Falls.  Photo by Charlie Davis.

Broader Impacts

The findings of BES have contributed to education of underserved communities, ecological urban design and planning, and discovery and valuation of ecosystem processes within the urban matrix from city to exurb.  Most fundamentally, BES has documented the existence and mechanisms of ecosystem processes in complex urban environments.  The BES research platform is poised to help inform, evaluate, and educate about the sustainability initiatives now being implemented in the Baltimore metropolitan region.

Swamps and the City

Laura A. Ogden, of Florida International University is an anthropologist and Co-Principal Investigator of the Florida Coastal Everglades LTER.  She is also a regular collaborator with the BES community and has been involved with us and others in cross site projects concerning environmental justice, and the social ecology of lawns.  She has additional projects addressing land cover change, political ecology, and vulnerability to hurricanes, among others (http://fcelter.fiu.edu/about_us/personnel/profiles/index.htm?resnum=156&display=projects).  So her recent book, entitled Swamplife: People, Gators, and Mangroves Entangled in the Everglades (2011, Univ. of Minnesota Press, Minneapolis), is of interest to our community.

Photo by Deborah Mitchell.  

 

Ogden’s book ranges widely, dealing with how Native American peoples, white alligator hunters, scientists, conservationists, and even outlaws, created various conceptual and literal landscapes in the Everglades.  The reciprocity of the natural – alligators, snakes (real and imagined), mangroves, hydrological fluctuations, and fire, with the human – lifeways, laws, territorial claims, the politics of scientific exploration, and the establishment and enforcement of state and national parks, are all part of swamplife.  This concern with the hybridity of landscapes in the Everglades parallels our conceptualization of the Baltimore region.

Hybrid Landscapes

Even though the Everglades is now and has always been a hybrid human-natural system, as Ogden so engagingly shows, mainstream or outside culture has neglected or erased much of the entangled human history and intimate inhabitation of the Everglades.  Reading this book is a trip through several good yarns, interesting interviews with people who once made their living by hunting in the ‘Glades, and documentation of how some key habitats came to be considered wild and imminently conservable.  For example, Royal Palm Hammock was seen by early scientific explorers as a pristine tropical outlier, untouched by human history.  Any Indian effects were disregarded as having been essentially a part of the wild landscape.  However, the hammocks, as high ground in a watery ‘scape, were precious sites for all who occupied, lived in, traversed, or made their living in the Everglades.  Such was the case prior to European contact and through the early 20th century when even the poor white residents were finally dispossessed to establish the national park.  Indeed, the intensity of human entanglement with the hammocks is illustrated by the evidence that many were at least partially constructed by accretion of the debris of people’s everyday life before the historic record began. 

Overcoming Erasure

Much of the academic and practical approach to the Everglades has intentionally or accidentally erased the human side of the story.  Ogden succeeds in bringing the human history of the Everglades and its erasures to light.  She puts the humans back in the picture.  She also highlights the role of class as well as ethnicity in such erasures.  

Overcoming human erasure parallels one of the big tasks we have in the Baltimore as well.  Urban systems have been predominantly seen as strictly human places.  Of course there are deep roots of knowledge about the entanglements of nature in cities.  But the weight of the academy has been on the human side of the scale.  We, like Ogden in Swamplife, struggle to understand how humans and nature are entangled in the system we study.  However, in the City-Suburban-Exurban system the erasure has been opposite to the one she overcomes in her book.  We are peeling back the assumptions that have allowed people to erase the natural in the city.  So there are many ways in which the city and the swamp are fighting the same intellectual battles.  People and nature go together, whether in town or out.

Urban Ecology: Use and Abuse

In the first two decades of the 20th century, two new scholarly disciplines were being established in the United States. One was the biological science of ecology, and one was sociology. Although both had deeper European roots, and began to flourish in several American universities, there was one school that was a seedbed for both: the University of Chicago. Historian Jennifer S. Light examines the relationship of these two disciplinary schools and the decades long ramifications of that intellectual hybridization on American urban policy (Light 2009). Her book is much richer in insights about urbanism and the linkage of ecology and policy than can be represented in a brief essay, so I encourage people to peruse her work directly.

The biological ecologists at the University of Chicago had been instrumental in elucidating the patterns and processes of change in plant communities through time. Chicago’s Henry Chandler Cowles in 1899 had published a long, multi-part paper that described the succession of plant communities on the dunes at the southern end of Lake Michigan (Cowles 1899). As the land was still rising in elevation, rebounding from the weight of the thick glaciers that had melted away some 12,000 years previously, new sandy substrate was exposed at the margin of the lake. Cowles (pronounced like the stuff burned in a furnace) described the ever taller and more complex plant communities that occupied the bands of surfaces that were located farther and farther from the lake shore.

The kinds of patterns that Cowles described as one moves from the lake shore inland were generalized by Frederick E. Clements (Clements 1916). Clements generated a theory of succession, in which he proposed that plant communities experienced progressive trends of change, leading to a diverse, stable assemblage. He likened the temporal patterns of change in assemblages of plants in the field to the life cycle an organism. Communities of plants were said to go through phases of colonization, growth, and maturation (Pickett and Cadenasso 2005).

A version of Clements’ theory was enthusiastically adopted by he Chicago sociologists in their attempt to understand their rapidly changing metropolis (Light 2009). They saw the city as a series of rings surrounding downtown, in which new immigrants invaded near the commercial core, and through competition moved outward. Like the first theory of plant succession, the sociological explanation of spatial pattern was considered to be a set life cycle. However, one important difference was that the sociologists substituted a decadent, blighted community as the end point as opposed to the idealized diverse, tall, and spatially complex “climax” forest.

The sociologists were apparently unaware of problems that were emerging with the theory of succession in biology (Miles 1979). Cowles’ original assumptions had some problems – sites that had better developed plant communities on the lake shore transect in some cases turned out to be different in other ways than just age of the substrate. Furthermore, Clements’ grand theory of succession as the life cycle of an organism was ultimately found to too rigid and methodologically problematical. Succession actually involved much variety in the patterns of change, and the mixture of causes was much more contingent on history and the landscape context than the developmental biology of individual organisms. The progressive theory of succession formulated by Clements was in dispute as early as 1917, and alternative views of the causes and patterns of succession were being worked out by a number of plant ecologists, some elsewhere in Illinois (Gleason 1917).

Why were the Chicago School sociologists so enamored of the life cycle metaphor they took and modified from ecology? Chicago had doubled in population in the early years of the 20th century, and was absorbing massive numbers of migrants from the American South and from Southern and Eastern Europe. These migrants represented groups that had largely been absent from Chicago before. They saw the effects of these waves of migrants as a succession that led to blighted neighborhoods. Slums and social pathologies were identified as problems to be solved by identifying where a neighborhood was in its life cycle, and intervening to counteract any tendencies toward blight.

Several kinds of intervention were possible. One social intervention was exemplified by the work of “settlement houses,” which were intended to introduce new migrants to values held by the predominant antecedent culture of a city. Another intervention was to attempt to keep some neighborhoods from changing to accommodate new migrants. This was accomplished by discriminatory laws or discriminatory lending practices. A third was urban planning, which could in cases where blight had proceeded beyond tolerable limits, be employed to clear slums and install new housing and neighborhood layouts intended to promote desirable social interactions. Light documents the intellectual lineages, the persistence of the life cycle approach, and the pervasive effects of this perversion of ecological thinking on the form of late 20th century American cities.

What Does This Mean for BES?

One lesson for an interdisciplinary research program emerges from Light’s analysis. The ecology that was used by the Chicago School sociologists was a superficial metaphor. Communities changed through time, that change was driven by competition, and expressed itself in an inexorable life cycle. The real mechanistic complexity that was emerging from scientific research in biological ecology was not apparently known to the Chicago sociologists. The metaphor was established in sociology through reading of ecological texts, but apparently not through conversation with practicing bioecological researchers. The complexity, the controversy, and the alternative models of vegetation change did not become part of the toolkit of the social science deployed to understand rapidly changing cities. Nor were these features of understanding community and spatial dynamics available to those who shaped federal policy of urban life cycles – the policy that supported urban renewal.

Although metaphor is a powerful bridge between disciplines, and from disciplines to application, substantive dialog between researchers and practitioners who know the frontiers of their disciplines is a sounder link. Analogy and metaphor are only tools for starting the dialog. Light provides a compelling analysis that will be of value to all urban researchers and practitioners.

References Cited

Clements, F. E. 1916. Plant succession: an analysis of the development of vegetation. Carnegie Institution of Washington, Washington.

Cowles, H. C. 1899. The ecological relations of the vegetation on the sand dune of Lake Michigan. Botanical Gazette 27:95-117,167.

Gleason, H. A. 1917. The structure and development of the plant association. Bulletin of the Torrey Botanical Club 44:463-481.

Light, J. S. 2009. The nature of cities: ecological visions and the American urban professions 1920-1960. Johns Hopkins University Press, Baltimore.

Miles, J. 1979. Vegetation dynamics. Wiley, New York.

Pickett, S. T. A. and M. L. Cadenasso. 2005. Vegetation succession. Pages 172-198 in E. van der Maarel, editor. Vegetation Ecology. Malden, MA, Blackwell Publishing.

Photo by Brian P. McGrath.